In a precast open bottom culvert system, for example, as disclosed in U.S. Pat. No. 4,993,872 which issued to the assignee of the present invention, the handling and shipping restrictions with respect to weight, height and width of each precast open bottom one-piece culvert unit has limited the maximum span for a culvert system. For example, with a culvert system having a span above 48 feet, the weight, height and length of each one-piece culvert unit present problems with shipping the unit along a roadway on a low bed semi-trailer.